To express 0.8 as a fraction in simplest form, you can follow these steps:

Step 1: Write the decimal as a fraction by placing the decimal value over a power of 10. In this case, 0.8 can be written as 0.8/1.

Step 2: Multiply both the numerator and denominator by 10 to remove the decimal. This gives us 8/10.

Step 3: Simplify the fraction by finding the greatest common divisor (GCD) of the numerator and denominator, which is 2 in this case. Divide both the numerator and denominator by the GCD to get the simplest form.

Dividing 8 by 2 gives us 4, and dividing 10 by 2 gives us 5.

Therefore, 0.8 as a fraction in simplest form is 4/5.